1. Field of the Invention
The present invention relates to a cable with a waterproof plug, a connector cable with a waterproof plug, a manufacturing method of a cable with a waterproof plug, and a connection structure between a cable with a waterproof plug and a terminal.
2. Description of Related Art
Connectors used in cars, portable devices, etc., are required to be waterproof for preventing water or the like from entering to cause a short circuit.
Cables used for connectors are generally classified into cables substantially circular in cross section and cables substantially rectangular in cross section such as flexible flat cables (FFCs) and flexible printed circuits (FPCs). The former and the latter differ in manner of being attached to connector housings.
In case of cables substantially circular in cross section, in general, a terminal is connected to one end of a cable and the terminal is inserted into a terminal receiving chamber formed in a connector housing. To give waterproofness to such a cable, for example, JP-A-7-245149 discloses a technique in which a waterproof plug is interposed between the cable and a terminal. In this technique, the waterproof plug has a crimp connection portion at its one end and a seal portion at its other end. After the waterproof plug is fitted on one end portion of the cable, one end of the terminal is wound on the outer circumferential surface of the connection portion of the waterproof plug and then the one end of the terminal is crimped. The connection portion of the waterproof plug is thereby also crimped with the one end of the terminal, so that three of the cable, waterproof plug, and terminal are fixed to one another. In this state, the terminal is inserted from its other end into a terminal receiving chamber of a connector housing. The outer circumferential surface of the seal portion of the waterproof plug is brought into close contact with the inner surface of the wall of the terminal receiving chamber so that water or the like can be prevented from entering the terminal receiving chamber.
In the above-described technique, however, the connection portion of the waterproof plug must have a sufficiently large thickness in order not to be broken when being crimped. Further, the seal portion of the waterproof plug has its outer diameter larger than that of the connection portion. In case of a connector provided with cables each having such a waterproof plug, therefore, the cables must be arranged at relatively wide intervals. This makes it difficult to attempt a decrease in size of such a connector.
Further, in the above-described technique, the cable and the waterproof plug are not fixed to each other before being crimped. They are fixed to each other by crimping. Thus, the waterproof plug may shift from its predetermined position when being crimped. This causes a problem of bad positional accuracy of such a waterproof plug.
Furthermore, in the above-described technique, one end of the terminal is made into a form that can be wound on the outer circumferential surface of the waterproof plug. However, if the cable has no need of waterproofness, that is, if no waterproof plug is used, a terminal must be used whose one end is made into another form, for example, that can be wound on the outer circumferential surface of the cable. Thus, terminals having different shapes must be prepared for cases of requiring waterproofness and not requiring waterproofness. This causes a problem of an increase in cost.
On the other hand, in case of cables substantially rectangular in cross section such as FFCs and FPCs, in general, a cable itself is inserted into a connector housing with using no terminal. To give waterproofness to such a connector structure, a technique is known in which a gelatinous sealing agent is interposed between the cable and the inner surface of the connector housing. However, such a gelatinous sealing agent can not be reused after the cable is detached from the connector housing. Thus, a fresh sealing agent must be used every time when the cable is attached to the connector housing. This causes an increase in cost.